Filter for high-frequency oscillations



Oct. 9, 1928.

H. J. J. M. DE R. DE BELLESCIZ E FILTER FOR HIGH FREQUENCY OSCILLATIQNSFiled June 2, 1925 vwamtoz H-J-J- DER. 'DE-BELLESCIZE @51 M15, Elam/m1;

FREQUENCY Patented 9, 1928.

UNITED STATES 1,687,062 PATENT OFFICE.

HENRI JEAN JOSEPH MARIE DE REGNAULI) DE BELLESCIZE,-OF TOULON, FRANCE.

FILTER FOR HIGH-FREQUENCY OSCILLATIONS.

Application filed June 2, 1923, Serial No. 642,883, and in France June8, 1922.

The present invent on relates to animproved method of coupling aplurality of resonant circuits cascade fashion, and more particularlyrelates to securing a purely inductive coupling between such circuits.My invention is illustrated in the attached drawing in which i Fig. 1shows an arrangementof tuned circuits in cascade as used in radiosignalling systems,

Fig. 2 shows a similar system as con= structed in accordance with myinvention,

Fig. 3 shows such a system provided with a closed antenna, and

Fig. 4c is a comparison of resonance curves of the old and newarrangement.

The disposition in cascade of several tuned-or resonant circuits hasbeen resorted tOfOr a long while in the construction of receivingapparatus in wireless work. This arrangement which at equal syntony,per-" mits of reducing. the duration of establishment and extinction ofoscillations, shows a tendency of becoming more general in use andapplication under the name of filters. Now, in order to realize goodresults it is indispensable that the coupling existent between the twoconsecutive resonators, no

matter of what sort they may be, should not be at the same timeinductive and electrostatic (or capacitative).

In Fig. 2 of the drawing in which is illustrated, by wayof example, myinvention applied to a filter,C,, represents a conventional aerialconnected to ground through the inductance L and the coil m. The coil mis in inductive relation to the coil M to induce oscillations,corresponding to those in the l antenna circuit, in the resonant circuitM, 0,.

This latter circuit is inductively connected in cascade to the resonantcircuit L G which in turn is inductively coupled to the resonant circuitL C The relation of the coupling coils in each ofthese circuits is isnot confined to the modes of execution as exactly similar, and it willbe necessary'tO describe the arrangement with respect to the circuit M,C, alone.-

The coupling coils m,M' are placed end to end in. inductive relationshipand their adjacent ends are grounded to fix the potential at thesepoints. That is, the point Q in the coil M is grounded and the point 0in, the coil m is grounded. From this arrang'ement. it follows that thepotential between ground and any point in the coil M is proportional tothe distance between that point and the coil m. In other words, thehigher the potential of a point in the coil M above ground potential,thegreater will be its dstance from the coil m and as the capacitybetween the coils is inversely proportional to the distance separatingthem the capacitative efiects along coil M decrease as the potentialincreases, thereby reducing the capacitative coupling between the coilsM, mto a minimum.

The arrangement in Fig. 3 is substantially the same as that in Fig. 2,except that the aerial C is replaced by a closed antenna circuitcomprising the inductance L and the condenser C The operation of thisdevice is, of course, the same as that of the device riod of excition atthe input end of the filter device is caused to be varied, the resonancecurve observed at the output end assumes the regular shape of curve a(Fig. 4) whereas when cutting off the various equipotential connectionspreviously described (which substantially is tantamount to theemployment of the customary mode of mounting as illustrated in Fig. 1),a curve is obtained having a shape substantially as curve I), Fig. 4.

The imput resonator, i. e., resonant circuit,

may consist of either an open oraclosed antenna (Fig. 2 and Fig. 3respectively). The

resonators, with the exception of the antenna, can be enclosed in ametal cage X, which sh elds and protects them from the direct action ofHertian waves. The said metallic box could also be subdivided orpart'tioned by means of partitions Y likewise consisting of metal, tothe end of enclosing each coil L in its own Faraday cage,

which'safeguards it from residual or stray electrostatic actions due toother coils. cages themselves could earthed.

The invention itself, be it Well understood,

The

described my invention, what I secondary coupling coil, the primary oneof said circuits being connected end to end with 'mon connection of theprimary and secondary.

2. In a cascade circuit arrangement, a plurality ofresonant circuits,each having primary and secondaryinductance coils, one end of eachprimary and its associate secondary in the next successive resonantcirncemcee cuit being connected to a common ground,

the arrangement being such that the potential at any point in saidinductances is directly proportional to the distance between said pointand the common ground connection, thereby substantially reducing thedistribu tive capacity between said primary and secondary inductancecoils.

HENRK JEAN JOSEPH MARIE cle REGNAULD de BELLESCIZE.

